1. Field of the Invention
The present invention relates to a display device and a manufacturing method therefor, and more particularly, to a display device including thin-film transistors or the like on a substrate forming a display section, and a manufacturing method therefor.
2. Description of the Related Art
In an active matrix liquid crystal display device, for example, gate signal lines and drain signal lines are formed on a liquid crystal side-surface of one of a pair of substrates arranged to face each other while sandwiching liquid crystal therebetween. The gate signal lines extend in an x direction and are arranged in parallel to one another in a y direction. The drain signal lines extend in the y direction and are arranged in parallel to one another in the x direction. Rectangular areas surrounded by the gate signal lines and the drain signal lines are each referred to as pixel area.
Each pixel area includes at least a thin-film transistor which is driven by a signal (scanning signal) from the gate signal line, and a pixel electrode supplied with a signal (image signal) from the drain signal line through the thin-film transistor. The pixel electrode generates an electric field which drives the liquid crystal, with a counter electrode formed on one substrate on which the pixel electrode is formed or on another substrate which is disposed to face the one substrate.
In this case, a capacitor element is generally formed in each pixel so that the image signal is stored in the pixel electrode for a relatively long time. The capacitor element includes one electrode electrically connected to the pixel electrode, and another electrode electrically connected to a capacitor signal line which is simultaneously formed with a formation of, for example, the gate signal line. The capacitor signal line is supplied with a reference signal which serves as a reference with respect to the image signal.
Further, the insulating film which serves as the dielectric film of the capacitor element uses the same insulating film formed as the gate insulating film of the thin-film transistor. Therefore, the dielectric film of the capacitor element and the gate insulating film of the thin-film transistor are formed of the same material and with the same film thickness (see Japanese Patent Application Laid-open No. 2002-182239).
Note that, in some liquid crystal display devices, a scanning signal drive circuit for supplying the scanning signal to the gate signal line and an image signal drive circuit for supplying the image signal to the drain signal line are formed at a circumference of the display section on the same substrate. The scanning signal drive circuit and the image signal drive circuit include a plurality of thin-film transistors formed in parallel to the formation of the thin-film transistors formed in the pixels.